As is known, some widespread types of amplifiers, for example class D audio amplifiers, exploit full-bridge converter stages in order to maximize the dynamics of the output voltages that may be supplied to the load, maintaining high efficiency.
A full-bridge converter stage of an audio amplifier is based upon two half-bridge circuits, which may be controlled separately, albeit in a coordinated way, by respective distinct driving stages. This type of technology affords in fact a satisfactory flexibility of use. For instance, it is possible to implement pulse width modulation (PWM) techniques, both in phase and in phase opposition.
The driving stages have the same structure and receive at input signals in phase opposition that are used for controlling the respective half-bridge circuits symmetrically.
A limit of known amplifiers that are based upon independent driving stages is represented by the rejection of common-mode disturbance.
Possible defects of symmetry of the two driving stages may easily lead to unbalancing that affects the rejection of supply disturbance and cause so-called “crosstalk” phenomena.
Furthermore, known structures suffer from a certain sensitivity to high-frequency noise, which is typical of analog-to-digital converters of a sigma-delta type, which are frequently used upstream of the stages for driving the final power stages.
Known technology for overcoming the sensitivity to high-frequency disturbance lead on the other hand to an increase in the number of components and, consequently, in the complexity of the amplifiers.